This invention relates to radiating elements and antennas and, more particularly, to double-tuned elements economically fabricated from sheet stock and usable in linear array antennas for cellular applications.
For a variety of reasons it is desirable to provide highly reliable, low cost antennas suitable for meeting the requirements of cellular communication applications. As a result of operational characteristics and signal levels of cellular systems, spurious intermodulation effects which may be produced in antennas at electrical contact points are particularly undesirable. Contact points or physical connections existing where radiating elements are interconnected or are connected to feed lines may give rise to such intermodulation products. Intermodulation product (IMP) problems may thus result from bimetallic contacts, corrosion effects over time, and combinations of materials resulting in contact points with semiconductor-like characteristics.
While simplicity of construction and low cost construction are common objectives in antenna design, in cellular applications such objectives may be directly consistent with considerations important to achieving the lowest levels of intermodulation effects. Thus, complex antenna designs relying on assembly of many components may provide a variety of possible sources of intermodulation effects. Conversely, if a simple one-piece radiating element construction could be provided with a reduced number of component contact points, sources of intermodulation effects would be avoided. At the same time, benefits of low cost and ease of assembly could also be achieved. Many of these objectives are achieved in U.S. Pat. No. 5,742,258, titled "Low Intermodulation Electromagnetic Feed Cellular Antennas" and commonly assigned with the present application.
Objects of the present invention are to provide new and improved radiating elements and antennas utilizing such elements having one or more of the following advantages and characteristics:
simplified one piece construction; PA1 integrated configuration including radiating, exciter and balun sections; PA1 double-tuned radiating element with simplified onepiece configuration; PA1 two step fabrication, stamp from sheet stock and provide a single 90 degree bend; PA1 broad-band, double-tuned operation; PA1 radiating section, exciter section and balun section stamped in one piece from conductive sheet stock; and PA1 self-supported rectangular radiating section bent to position normal to antenna ground plane surface.